I have a batch of mice samples fixed in neutral buffered formalin, and they are for immunochemistry and histology purpose. How can I properly keep them for 3 months or longer?
If you would like to keep for long time such as 3 months, you can keep the tissue as paraffin embedded (to cut sections through microtome) or frozen samples (to cut sections through cryostat).
Both the protocols are very simple and are available in online.
Xian,
I would keep them refrigerated and refresh the solution every few days. Remember the formalin only crosslinks proteins, with time your lipids will be gone. Also the crosslinking of formaldehyde is reversible if left in a buffer.
good luck,
If you would like to keep for long time such as 3 months, you can keep the tissue as paraffin embedded (to cut sections through microtome) or frozen samples (to cut sections through cryostat).
Both the protocols are very simple and are available in online.
Depending on your aims and following procedures I would prefer to make paraffin blocks. This supports that your samples have nearly the same fixation-time and makes your experiments more standardized. Antigens that can be demonstrated via HIER induced IHC are usually well preserved in paraffin blocks. To prepare sections long before the actual staining is not recommended. Slides should be stained within a week after sectioning.
If you plan to do frozen sections of your specimen I would recommend to cryo-protect and freeze. Make a search for this procedure.
Depending on the tissue and the future aim, several methods are available.
If it is a block of tissue, I used either parafin embedding, freezing after cryoprotection, or phosphate buffer with azide in the freedge.
If the sample are already sections obtained via a vibratome or freezing microtome I put them in a cryoprotectant and freeze them.
As cryoprotectant I use 25% sucrose solution or 30% glycerol-30% ethylene glycol-40% 0.IM PBS solution or 25%glycerol-30%ethyleneglycol-45% PBS solution.
Hallo Xiang, as all other collegues told already, it depnds on what you like to do with your tissue. To prepare paraffin locks is a good idea when you have decided to work with thin sections (3-6 µm). If you like to work with frozen or vibratome sections then I recommand to stop the fixation and put the blocks in 30% sucrose at 4°C until they sunk. The sections (around 30 µm thick) you can store for more then a year in a solution containing 30% sucrose and Glycerol each parts (Catherine recommands similar protocols) at -20°C. Most antibodies work on such prepared tissue. Good luck!
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